1. Field of the Invention
The present invention relates to a heat treatment apparatus and a heat treatment method for heat treating a semiconductor article in the production of a semiconductor device for integrated circuits. The present invention also relates to a process for producing a semiconductor article.
2. Related Background Art
In the production of a semiconductor device, a heat treatment apparatus is used in a process of forming an oxide film or diffusing an impurity as a donor or an acceptor and in a process of annealing a semiconductor article such as a bulk Si wafer in a hydrogen-containing reducing atmosphere.
FIG. 9 shows a first example of a heat treatment apparatus of the prior art. This heat treatment apparatus has inner tube 1 and outer tube 2. A hydrogen-containing reducing gas GH is introduced from inlet 5 and is discharged through vent 6. Into the interspace between inner tube 1 and outer tube 2, an oxygen-containing gas Go is introduced through inlet 7 and is discharged through vent 8 to prevent penetration of copper (Cu) from the outside into inner tube 1. The symbol W indicates an Si wafer. The numeral 4 indicates a boat. Such an apparatus is disclosed in Japanese Patent Application Laid-Open No. 5-152309.
FIG. 10 shows a second example of a heat treatment apparatus of the prior art. This heat treatment apparatus comprises inner tube 1 made of silicon carbide (SiC), heater 3, and therebetween an open-ended outer tube 2 made of fused quartz produced by an oxyhydrogen flame fusion method and containing OH groups at a content of 200 ppm. The outer tube prevents diffusion of metal impurity. Such an apparatus is disclosed in Japanese Patent Application Laid-Open No. 7-193074.
FIG. 11 shows a third example of a heat treatment apparatus of the prior art. This heat treatment apparatus comprises inner tube 1 made of SiC and outer tube 2 made of fused quartz. An oxygen-containing purge gas is introduced into the interspace between inner tube 1 and outer tube 2 through inlet pipe 7 and is discharged through vent pipe 8. A cooling gas is introduced through inlet pipe 10 and is discharged through vent pipe 11. The numeral 9 indicates a table which serves as a heat barrier. Such an apparatus is disclosed in Japanese Patent Application Laid-Open No. 8-31761.
FIG. 12 shows a fourth example of a heat treatment apparatus of the prior art. This heat treatment apparatus comprises inner tube 1 and outer tube 2, both made of fused quartz, and heat equalizer tube 20 between outer tube 2 and heater 3. An oxygen-containing gas is introduced from gas inlet pipe 12 at the bottom to the interspace between inner tube 1 and outer tube 2, further introduced to the inside of inner tube 1 through plural gas inlet holes 5, and discharged from vent pipe 6. The numeral 13 indicates a heat insulating material. Such an apparatus is disclosed in Japanese Patent Application Laid-Open No. 7-161655.
FIG. 13 shows a fifth example of a heat treatment apparatus of the prior art. This apparatus comprises inner tube 1 made of SiC and outer tube 2 made of fused quartz. A treating gas like an oxidizing gas is introduced from inlet 5 at the bottom into inner tube 1, further introduced through communication hole 13 into the interspace between inner tube 1 and outer tube 2, and discharged from vent 6. Such an apparatus is disclosed in Japanese Patent Application Laid-Open No. 7-302767.
However, the apparatuses of the prior art have problems of contamination, treating gas leakage, reaction tube deformation, reaction tube cracking, and so forth, which have not been solved.
On the other hand, it was found by the inventors of the present invention that by conducting heat treatment in a hydrogen-containing reducing atmosphere, semiconductor articles are etched undesirably.
An object of the present invention is to provide a heat treatment apparatus, a heat treatment method, and a production process for semiconductor articles in which the metal contamination caused by the metal of a reaction tube is reduced.
Another object of the present invention is to provide a heat treatment apparatus, a heat treatment method, and a production process for semiconductor articles in which gas leakage caused by reaction tube deformation is prevented.
A further object of the present invention is to provide a heat treatment apparatus, a heat treatment method, and a production process for semiconductor articles in which undesired etching is prevented.
According to an aspect of the present invention, there is provided a heat treatment apparatus which comprises a first tube, a second tube placed therein, and a heater. The first tube can be tightly closed and is made of vitreous silica having an impact strength higher than that of the second tube. The second tube has at least an internal face comprised of non-silicon oxide, and a gas flow path is constructed to introduce a gas into a treatment space in the second tube without passing over a face comprised of silicon oxide heated to a high temperature by the heater.
According to another aspect of the present invention, there is provided a heat treatment apparatus comprising a first tube, a second tube placed therein, and a heater. A gas inlet for introducing the gas in the second tube is provided below the heater, a hole for communicating the first tube to the second tube is provided at a top portion of the second tube, a vent is provided at a bottom portion of the first tube for discharging the gas from inside of the first tube, the first tube is constructed from fused quartz and is able to be closed, the second tube has a non-silicon oxide surface and is able to be closed, and the heater is provided at higher level than a heat barrier placed in the second tube.
According to another aspect of the present invention, there is provided a heat treatment process for heat treating a semiconductor article by means of the heat treatment apparatuses set forth above.
According to a further aspect of the present invention, there is provided a process for producing a semiconductor article, the process comprising bonding a first base plate and a second base plate, eliminating an unnecessary portion of the first base member from the second base member, and heat treating a silicon body on the second base member in a hydrogen-containing reducing atmosphere by means of the above-mentioned treatment apparatuses set forth in above.